xref: /freebsd/contrib/llvm-project/libcxx/include/__compare/compare_partial_order_fallback.h (revision cb14a3fe5122c879eae1fb480ed7ce82a699ddb6)
1 //===----------------------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #ifndef _LIBCPP___COMPARE_COMPARE_PARTIAL_ORDER_FALLBACK
10 #define _LIBCPP___COMPARE_COMPARE_PARTIAL_ORDER_FALLBACK
11 
12 #include <__compare/ordering.h>
13 #include <__compare/partial_order.h>
14 #include <__config>
15 #include <__type_traits/decay.h>
16 #include <__type_traits/is_same.h>
17 #include <__utility/forward.h>
18 #include <__utility/priority_tag.h>
19 
20 #ifndef _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
21 #  pragma GCC system_header
22 #endif
23 
24 _LIBCPP_BEGIN_NAMESPACE_STD
25 
26 #if _LIBCPP_STD_VER >= 20
27 
28 // [cmp.alg]
29 namespace __compare_partial_order_fallback {
30 struct __fn {
31   template <class _Tp, class _Up>
32     requires is_same_v<decay_t<_Tp>, decay_t<_Up>>
33   _LIBCPP_HIDE_FROM_ABI static constexpr auto __go(_Tp&& __t, _Up&& __u, __priority_tag<1>) noexcept(
34       noexcept(std::partial_order(std::forward<_Tp>(__t), std::forward<_Up>(__u))))
35       -> decltype(std::partial_order(std::forward<_Tp>(__t), std::forward<_Up>(__u))) {
36     return std::partial_order(std::forward<_Tp>(__t), std::forward<_Up>(__u));
37   }
38 
39   template <class _Tp, class _Up>
40     requires is_same_v<decay_t<_Tp>, decay_t<_Up>>
41   _LIBCPP_HIDE_FROM_ABI static constexpr auto __go(_Tp&& __t, _Up&& __u, __priority_tag<0>) noexcept(noexcept(
42       std::forward<_Tp>(__t) == std::forward<_Up>(__u)  ? partial_ordering::equivalent
43       : std::forward<_Tp>(__t) < std::forward<_Up>(__u) ? partial_ordering::less
44       : std::forward<_Up>(__u) < std::forward<_Tp>(__t)
45           ? partial_ordering::greater
46           : partial_ordering::unordered))
47       -> decltype(std::forward<_Tp>(__t) == std::forward<_Up>(__u)  ? partial_ordering::equivalent
48                   : std::forward<_Tp>(__t) < std::forward<_Up>(__u) ? partial_ordering::less
49                   : std::forward<_Up>(__u) < std::forward<_Tp>(__t)
50                       ? partial_ordering::greater
51                       : partial_ordering::unordered) {
52     return std::forward<_Tp>(__t) == std::forward<_Up>(__u) ? partial_ordering::equivalent
53          : std::forward<_Tp>(__t) < std::forward<_Up>(__u)  ? partial_ordering::less
54          : std::forward<_Up>(__u) < std::forward<_Tp>(__t)
55              ? partial_ordering::greater
56              : partial_ordering::unordered;
57   }
58 
59   template <class _Tp, class _Up>
60   _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t, _Up&& __u) const
61       noexcept(noexcept(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<1>())))
62           -> decltype(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<1>())) {
63     return __go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<1>());
64   }
65 };
66 } // namespace __compare_partial_order_fallback
67 
68 inline namespace __cpo {
69 inline constexpr auto compare_partial_order_fallback = __compare_partial_order_fallback::__fn{};
70 } // namespace __cpo
71 
72 #endif // _LIBCPP_STD_VER >= 20
73 
74 _LIBCPP_END_NAMESPACE_STD
75 
76 #endif // _LIBCPP___COMPARE_COMPARE_PARTIAL_ORDER_FALLBACK
77